Why Jet Engines Keep Getting Bigger

Ever since the advent of the jet, engines have been getting bigger and bigger. It's not just to support large and larger aircraft, or because of some unfounded idea that bigger is better. When it comes to jet engines, bigger actually is better. At least up until a point.

This fantastically concise video by the incomparable MinutePhysics explains the cold, hard math of the matter which essentially boils down to one core point. The bigger a jet engine is, the more efficient it is, because it will waste less energy in the process of adding to a plane's momentum. At least until drag starts to be a factor.

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According to some napkin math (which looks positively terrifying when MinutePhysics writes it out on screen), the optimal size for a jet engine is somewhere around 13 feet in diameter, a little bit bigger than the biggest jet engines we have right now. Of course there will always be other innovations that can make jet engines more efficient—like cleverly engineered gearboxes—and small-but-powerful engines will always make sense for fighter jets. But at some point the limiting factors are as simple as the laws of physics.

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